Self Changing Text Size

I have this problem whenever I change the size of the words, it change itself to (number).9999999. Sometimes it works normally, sometimes it will change itself. Example, I put the size of the word as 13, it will change itself to 12.9999999,or if I put 15 it will change to 14.9999999. Whichever number I put it will sometimes change to self to the (number).9999999.

I'm also getting another problem. Example, if I set the number as 20, I saved it and ( I did not closed it, just minimized it ) went to other Prototypes. And when I come back to the same Prototype, the word's size on the screen is the same but the number on the upper bar and the properties are different, it can be other numbers. It will need a few tries to set back.